The present invention relates to a method of making a standard size photographic print, and more particularly, to a method of correctly adjusting the size of prints to a desired standard size.
In conventional photographic printers, the leading end of a withdrawn part of a photographic paper in the form of a roll is, after exposure at an exposure station of the printer, further withdrawn to a cutter and cut by the cutter to a separate print. The photographic paper is thereafter rewound or moved back so that the leading part of the photographic paper is positioned at the exposure station for another exposure. One such printer is described in, for example, Japanese Utility Model Registration Publication No. 62-13,073. The printer described in the Publication is conveniently used, in particular, to intermittently make a small number of prints or to make relatively large size prints such as quarter size (254.times.305 mm) prints. It is well known to incorporate in the printer a variable masking frame which changeably defines an exposure area for the photographic paper so as to make various sizes of prints.
Pulse motors are used to drive a photographic paper transport mechanism and a variable masking frame adjusting mechanism independently from each other so as to make various standard sizes of prints. Because of various errors in assembling component parts, dimensional and/or functional errors or changes of the component parts, changes of the component parts due to age, and the replacement of the component parts, a practical printer does not always adjust prints to desired standard sizes.
More specifically, rollers for transporting the photographic paper will be subjected to changes in friction coefficient and worn due to slippage caused therebetween or between the photographic paper. This leads to substandard size prints.
To avoid the occurrence of such an error, the number P.sub.f of pulses applied to a pulse motor for transporting a photographic paper is obtained as follows: EQU P.sub.f =.alpha..times.P.sub.fo
where .alpha. is a correction value; and
P.sub.fo is the number of pulses applied to the pulse motor. PA1 P.sub.mo is the number of pulses applied to the pulse motor. PA1 .gamma. is a correction value. PA1 .gamma..sub.c is a correction value common to all print sizes; PA1 .gamma..sub.p is a correction value for a specific print size; and PA1 K5, K6 is a constant which is any integer including 0 (zero).
The correction value .alpha. is individual to the printer and determined based on the ratio of an actual or apparent length X of a print relative to a desired length X.sub.o of the print. The number of drive pulses P.sub.fo is determined by dividing a length d.sub.f by which the photographic paper is practically transported by a distance d.sub.fo of movement of the photographic paper per pulse theoretically designed.
A variable masking frame unit includes a pair of masking members that are connected to and driven by a pulse motor through a timing belt so as to move apart from and close to each other, thereby changing the size of a masking opening of the variable masking frame unit. Because of an assembling error, the variable masking frame unit is sometimes incorrectly adjusted in mask opening size, resulting in a substandard size print.
For this reason, the mask opening of the conventional variable masking frame unit is adjusted by correcting the number of pulses applied to the pulse motor by using the following expression: EQU P.sub.m =P.sub.mo +.beta.
where .beta. is a correction value; and
The correction value .beta. is individual to the printer but independent from print sizes, and defined by dividing the difference (M-M.sub.o) between the length M of an image area of an actual print and the desired length M.sub.o of an image area of the print by a value as great as a distance d.sub.m per pulse by which the pair of frame members moves apart from or close to each other. The number P.sub.mo of drive pulses is defined by dividing a distance which is required for each of the pair of frame members to move from a reference or original position of the frame members to a position where the frame members form a desired masking opening by the distance d.sub.m per pulse.
The variable masking frame unit is so constructed as to vary the size of a masking opening by shifting frame members with respect to their reference positions and the photographic paper is moved by a distance that is determined on the basis of the reference position. A position sensor is provided to the masking frame member at the reference position. Due to the fact that a location where the position sensor is assembled in the printer is sometimes different from a theoretical or designed position or that the center of the masking opening of the masking frame unit is not always identical with the axis of a printing optical system, prints made by the printer result in having image areas different in position from the prints from one another and, having therefore different widths of front and rear end margins. Such position error can be avoided by adjusting a distance by which the leading end of the photographic paper is moved back and a distance by which the photographic paper is forwarded to be cut. The following expression has been used to obtain an apparent distance D between the reference position where the masking opening is the largest and the cutter as a parameter for determining a transportation length of the photographic paper: EQU D=D.sub.o +.gamma.
where D.sub.o is a designed distance between the reference position where the masking opening is the largest and the cutter: and
A problem in association with the above-described manner, when correction values .alpha., .beta. and .gamma. are set for certain standard size print, is that errors in size still occur in different size prints. Therefore, it is impossible for the conventional printers to make prints meeting possible standard sizes.